At the same time, last week when Star Trek and WWZ shared a double feature, MoS still had a higher per theatre average. So, there was the potential if the would have done a true re-release with even a little advertising MoS would have seen a substantial bump last week as well.

We've been there but re-expanding (or re-releasing) a film rarely translates onto a huge bump of the average. Take The Avengers for instance, that got re-expanded last year over labor day week end. It's average the week end before it's re-release was $938 and it reached $1,121 after that. That's a meager 19% boost. And that's the kind of growth MoS could have only hoped for.

Rightfully so, I think WB decided that it was just not worth it. It would've been ridiculous to spend even more money on a film that costed them too much already and for what ? 2 more millions at best while marketing only would have cost them at least twice that amount of money (it's been rumored that Disney/Marvel spent an additionnal 5 millions, in advertising only, for the domestic re-expanding of The Avengers) ?

If the film was sitting at 298 millions and needed some boost to get to 300 millions it would've been a different story. But in terms of how the movie's number will be appreciated 291 or 293 millions is pretty much the same.